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5B Periodic Trends

Atomic radius is defined as half the distance between the nuclei of atoms of the same element that are joined by a single covalent bond.

Trends in Atomic Radius going down a group. 2 reasons

Atomic radius INCREASES. 1: A new shell is being added as we move down the table. 2: The screening effect of the extra electrons cancels out the pull of the growing nucleus.

Trends in Atomic Radius going left to right across a period. 2 reasons

Atomic radius DECREASES 1: Increasing nuclear charge due to an extra proton being added 2: There is no increase in screening effect as no new shell is being added

Electronegativity

A measure of an atom's ability to attract and hold electrons in a molecule. Will predict how atoms combine chemically. Linus Pauling developed the electronegativity scale.

Trends in Electronegativity going down a group. 2 reasons

Electronegativity DECREASES as we go down a group 1: Increasing atomic radius means the electrons are further away from the attractive force of the nucleus. 2: The screening effect of the inner negative electrons block the pull of the positive nucleus.

Trends in Electronegativity going left to right across a period. 2 reasons

Electronegativity INCREASES going across a period. 1: Increasing nuclear charge means the nucleus has a stronger hold on the electrons. 2: Decreasing atomic radius: as no new shell is being added the stronger nucleus can hold the outer electrons tighter

Ionization Energy

The first ionization energy of at atom is the minimum energy required to completely remove the most loosely bound electron from a neutral atom in a gaseous state. Noble Gases have the highest Ionization Energy levels, as they have full outer energy level

Trends in Ionization energy going down a group: 2 reasons

Ionization Energy DECREASES going down a group. 1: As atomic radius increases the electrons are further away from the nucleus. 2: The screening effect of the inner electrons cancels out the pull of the nucleus.

Trends in Ionization energy going left to right across a period: 2 reasons

Ionization Energy INCREASE going across a period 1: Increasing nuclear charge means the nucleus has a better hold on the outer electrons. 2: Decreasing atomic radius means that the outermost shell is closer to the nucleus and is therefore held tighter.

Reactivity of the Alkali Metals

Increases as we go down the group. All the elements have only 1 electron on their outer shell. Losing this electron gives them a full outer shell. This means they have a low ionisation energy and electronegativity.

Properties of Alkali Metals

1: Easier to cut as we move down the group. 2: Display more vigorous reaction with water as we move down the group. 3: Tarnish with air faster as we move down the group.

Halogens

Have the highest Electron Affinity

Electron Affinity

The amount of energy required to add an electron to a neutral atom to form a negative ion or anion. How strongly an atom attracts additional electrons

Trends in Electron Affinity going left to right across a period

INCREASES from left to right along a period 1. as energy level continues to fill it has a stronger attraction for the electrons.